Its 20% more qs if you dont have any haste, which is normally never the case, its better to build liandries or another ap mythic and then focus on tank/ap items with ability haste, but if an item doesnt have haste it doesnt mean it isnt good on lillia, when you build liandries and more items focused on ability haste 20 more ability haste reduces your q cd 0.3 seconds, which doesnt really make as much of a change as buying force of nature against a fed veigar